Trommel screen machines are known. They are used, for example, in recycling and sorting plants for separating material of different size, respectively graining. They offer altogether a wide range of application, for example for screening and classification of compost, in the recycling of tailings, for waste dump regeneration, screening of bark cuttings, shredded material, matured timber cuttings, tree cuttings, mixed construction waste, rumble, cinder, gravel, soils or the like.
With the trommel screen machines known so far it has to be seen as a disadvantage that as screened good only the good which is determined by the size of the openings in the screening drum has a defined particle size. The screened good which is conveyed out of the screening drum at its end in the direction of transport of the screening good, contains, as a rule, large amounts of oversized particles, so that this good has to be screened one more time, or has to be put altogether again in a comminution machine in order to get it in a certain, determined graining.
Thus the material finally leaving the screening drum has a particle size which can be assigned to a certain, determined size at about 90 percent. However, about 10 percent are obtained as oversized particles so that it is necessary to screen again or to put the complete good of this fraction to a comminution machine. This problem also occurs if a stone grit at the feeding hopper prevents certain oversized particles from entering. Here higher amounts of working time and energy occur which can also lead to the fact that the known trommel screen machines are only applied for pre-sorting, or are only used for screening good where the percentage of deviations from the graining described above can be neglected because they are too small.
This problem occurs in particular, for example, with trees from clearings, matured timber, cross-sills or the like comminuted, for example, by means of drum disintegrators or shredders. But also in the processing of tailings this problem is relevant.